The present disclosure relates to a vehicle driving system. In particular, the present disclosure relates to a vehicle driving system that switches a driving mode of a vehicle when slipping occurs.
To date, technologies have been proposed for switching a drive mode of a vehicle from a two-wheel drive mode (hereinafter, referred to as “2WD”) to an all-wheel drive mode (hereinafter, referred to as “AWD”) when a front wheel or a rear wheel slips and then continuing AWD for a predetermined all-wheel drive duration after a time at which the wheel stopped slipping. Such technologies can include calculating a slipping amount (the amount or the degree of slipping) on the basis of the difference between the front wheel velocity and the rear wheel velocity and determining a period over which an all-wheel drive duration is to be extended in accordance with the cumulative sum of slipping amounts each calculated when slipping occurred.
However, even if the slipping amounts are the same, the road conditions may differ considerably depending on the magnitudes of driving forces when slipping occurred. Therefore, by simply switching the driving mode of the vehicle in accordance with the cumulative sum of slipping amounts, it may be difficult to appropriately switch the driving mode of a vehicle. To be specific, there is a possibility that the driving mode may be switched from AWD to 2WD when the road surface has a low coefficient of friction (μ). In this case, vehicle stability may decrease. Moreover, there is a possibility that the driving mode may be switched from 2WD to AWD and AWD may be maintained for an unnecessarily long period even when the road has a high coefficient of friction (μ) and AWD is not necessary. In this case, the fuel economy and the economy of consumption of electricity (hereinafter, referred to as “driving efficiency”) may decrease.